In the container industry it is frequently desirable to provide some means for indicating whether or not a container, of the type having a reusable closure, has been opened after once being sealed, in order to know whether the contents may have been tampered with.
Many constructions have been devised for this purpose, however, they are not fully satisfactory and suffer draw-backs. For example, a well known metal beverage cap incorporates a detachable rim which is torn off and remains on the container neck when the cap is removed for the first time. This approach gives a clear indication of tampering, but the sharp edges on the removed cap, and the presence of the loose ring on the container neck, are objectionable. Some other approaches have incorporated tear strips which always require an extra operation on the part of the user; these usually require reading of instructions by the user, may have projecting elements which are liable to catch on clothing and other external objects, and may result in littering the ground in public places. Another group of tamper-indicating closure designs depends upon bulky or unusual container-neck-constructions, which must be used with the particular closure.